1. Field of the Invention
The present invention relates to a vehicle brake system which controls braking force applied to a vehicle wheel in response to a brake operation amount operated by an operator of the vehicle.
2. Discussion of the Related Art
As one of such vehicle brake systems for controlling a braking force applied to a vehicle wheel in response to a brake operation amount operated by an operator of the vehicle, a vehicle brake system disclosed in a patent document JP2007-62614A is exampled. According to this vehicle brake system disclosed in the patent document, an input piston and a master piston are separately supported in the master brake cylinder, keeping a predetermined interval (stroke) therebetween and in response to the movement of the input piston, a braking pressure is applied to a wheel brake cylinder based on an assisting pressure generated by an accumulator and a linear valve.
Further, the vehicle brake system according to the patent document indicates that it is assisting pressure limit when the assisting pressure reaches the hydraulic pressure generated by the accumulator and thereafter, the master piston is directly pushed by the input piston to pressurize brake fluid in a hydraulic pressure chamber of the master brake cylinder, thereby applying a braking force pressure to the wheel brake cylinder.
However, according to the invention described in the patent document (JP2007-62614A), after the assisting pressure reaches the assisting limit pressure and the input piston begins to directly push the pressure piston, the operator of the vehicle receives a reaction force corresponding to the hydraulic pressure in the reaction force chamber and further reaction force corresponding to the cylinder pressure from the master piston. Thus, the operator of the vehicle receives an increased reaction force according to this conventional system disclosed in the patent document.